Car Stereos: stereo loses memory, vw passat, station clock

Question
I have an aftermarket Rosen navigation stereo in my 2008 vw passat.  It worked fine but now loses memory of last radio station, clock, and volume level.  Also, if I am in ipod mode and I turn off the car, it will return to FM radio when I restart the car.  However, it will remember all the prior settings when put in ACC mode, but as soon as I start it, all is lost.  Now it does retain all of my preset radio stations.  It's driving me crazy and I cannot find any disconnected wires.  There are 2 yellow wires coming from the head unit, but only one is hooked into the harness.  The other has a quick connect terminal with a label reading "cdc batt" and is NOT connected to anything.  I have been suspecting a memory wire problem. Any help is greatly appreciated.

Answer
Hi Shawn,

CDC you can ignore -- it's short for CD Changer.

What's interesting to me is that your car is acting differently on start.  VW and Audi are notorious for being one of the only companies that don't turn off the power to the accessory wire whilst starting.

I would suggest getting a multimeter and testing your yellow constant wire while starting.  See if it's losing voltage.  If it is, there's your problem.  It's also possible that your deck stores FM memory in EEPROM and current CD position/current source/current volume/etc in memory that is lost on loss of power.

If you are still getting a clean 12V(ish) volts to your deck while starting, you can assume the deck's internal memory has taken a crap and will need replacement (if that matters enough to you).

Justin